Electrodeposition of nickel



of nickel possessing the Patented June 4, 1946 stories nLne'rnanarosl'noN or mo .11 2

Milton Kamila, Dayton, Ghlo,

Monsanto Chemical Company, a ation of Delaware No Drawing. Application in: o

Serial No. $23,808

Glaims. (Cl. 2941-49) This invention relates to a process and composition'for use in electrodepositing nickel characterized in that the resultant nickel plate, as deposited, is highly lustrous, dense and uniform; it is highly adherent and of improved ductility. More particularly, the present invention relates to new compositions for producing electrodeposits of nickel posseming the above-mentioned characteristics.

I have found that improved results are obtained in the electrodeposition of'nickel by having present in the electrolytic bath alkali metal or nickel salts of the polysulfonates ofthe highboiling product secured in the cracking of benzene into biphenyl or of a like high-boiling product which has been subsequently partially hydrogenated.

In the cracking of benzene to biphenyl there is obtained as by-product a high-boiling material distilling as follows:

C at 1st drop 370 5% 373 374 50% 382 60% 384 70% 387 80% 393 90% Approx. 400

m-Diphenylbenzene 50-60 p-Diphenylbenzene' About o-Diphenylbenzene About 10 Triphenylene 3-4 and may therefore be characterized as acomposition comprising approximately 83% to 93% of mixed isomeric diphenyl benzenes. Such a composition will be hereinafter referred to as biphenyl high-boiler. Nickel plating baths containing small amounts, preferably 3.5 percent, by weight (based upon the volume of solution) of nickel or alkali metal polysulfonates of biphenyl high-boiler yield adherent and ductile deposits of nickel which are characterized by high luster, density and uniformity.

The addition to nickel plating baths of small amounts, say 3.5 percent, of the nickel or alkali metal polysulfonates of partially hydrogenated biphenyl high-boiler likewise yields electrodeposits above-mentioned desirable characteristics. Thus, the biphenyl highboiler may be caused to react with hydrogen or an agent yielding hydrogen until from 40%. to or of the double bonds havebeen saturated, and the partially hydrogenated biphenyl high-boilers obtained in this manner are subsequently converted into their alkali metal or nickel polysulfonates. The partially hydrogenated biphenyl h-b'oilers are mixtures compris ing mainly isomeric monoand di-cyclohexylbenzenes, the proportion of these cyclohexylbenzenes depending upon the extent of hydrogenation.

As illustrative of the process for the preparation of the compounds of the present invention, biphenyl high-boiler which was 40% hydrogenated, is converted into polysulfonic acids and thence into the nickel polysulionates by the following procedure:

Approximately g. of the 40% hydrogenated biphenyl high-boiler and 150 g. of carbon tetrachloride are placed in a sulfonation flask, cooled by an ice bath-and sulfur trioxide (prepared by I heating 65% oleum in a sulfur trioxide generator) is passed in'until the weight gain is about 77 g. and loss in welg t of the oleum flask 15100.5 g. The sulfur trlo de generator is then uncoupled and dry air is blown through the whom.-

tor charge until all absorbed sulfur trioxide' is removed. Throughout the sulfonation and blowing operations a temperature of approximately 70 C. to 80 C. ismaintained. The solvent is then removed. and the product is converted to the nickel salt as by neutralization with nickel carbonate. The productwas thereafter drumdrled.

The sulfonates produced by the above process are believed to be polysulfonates, that is di-, tri-,

and tetra-sulfonates are present in the product.

When polysuli'onating a hydrocarbon mixture such as that herein treated, I prefer to carry the sulfonation to the point where the mixture co'n-.

tains on the average, sulfonation products equivalent to the tr'isulfonate. Where"sulfonation is conducted as described the product while containing largely trisulfonated hydrocarbons will also contain some proportion of the diand the terasulfonated product.

The nickel polysulfonate, largelytrisulfonate of 40% hydrogenated biphenyl high-boiler, thus obtained was evaluated as an adjuvant in the electrodeposition of nickel. For this purpose there was used a representative nickel bath, known as Watts solution, and comprising the following constituents:

3 Per cent Nickel sulfa 24.0 Nickel chloride 7.5 Boric acid 3.75 Water 64.75

To two liters of the above solution there was added '10 g. (3.5% by weight based upon volume of Watt's solution) of the nickel polysulfonate of this invention, and electrodeposition of nickel was effected under the following conditions:

Cleaning cycle before 4% trisodium phosphate Nickel plate obtained by the process of this invention is an adherent and ductile plate characterized by high luster, density and uniformity.

Nickel polysulfonates of other hydrogenated biphenyl high-boiler, e. g., 60% hydrogenated biphenyl high-boiler, or of biphenyl high-boiler, itself, may also be used for the purposes of this invention. Instead of thenickel salts herein described there may likewise be used alkali metal salts of polysulfonates of biphenyl high-boiler or of a partially hydrogenated biphenyl highboiler. The individual constituents of biphenyl high-boiler, e. g., o-. m-, or p-diphenylbenzene or synthetic mixtures of the same may be converted into nickel or alkali metal polysulfonates and added to nickel platingbaths for the production of adherent and ductile nickel plate which is characterized by high luster, density and uniformity. Likewise, the individual constituents of partially hydrogenated biphenyl high-boiler, e. g., 0-, m-, or p-monocycloalkyl biphenyl or o-, m-, or p-dicycloalkyl benzene or synthetic mixtures of the same may be converted into nickel or alkali metal polysulfonates and added to nickel plating baths for the production of nickel deposits having the above-mentioned desirable properties. Obviously, for economic reasons, the use of the biphenyl high-boiler or of the hydrogenated biphenyl high-boiler mixture is to be preferred.

It will be realized by those skilled in the art.

that changes may be made in the process of electroplating and in the composition of the electrclytes without departing from the invention. The compounds of the present invention may be used in the known acid nickel plating baths, with or without the use of other additives, e. g., antipitting and/or surface tension reducing agents, for the formation of adherent and ductile deposits of nickel whichare characterized by high luster, density and uniformity.

It will also be realized by those skilled in the art that changes may be made in the preparation of the nickel or alkali metal polysulfonates of this invention. Thus, the sulfonation need not be effected with sulfur trioxide; any of the wellknown' sulfonating agents, e. g., oleum, chlorosulfonic acid, etc., may be used for this purpose under such conditions as are best suited for sulfonating with the particular sulfonating agent employed. Neutralization may be effected with other basic compounds of nickel or by metathesis employing an alkali metal 01' ammonium salt with a soluble nickel salt.

What I claim is:

1. A nickel plating bath comprising essentially a water solution of nickel sulfate, nickel chloride and boric acid, containing as an organic brightening agent a mixture of polysulfonates of isomeric biphenyl benzenes, said agent being present in amount up to 3.5% by weight of said solution. I

2. A nickel plating bath comprising essentially a water solution of nickel sulfate, nickel chloride and boric acid, containing as an organic brightening agent a trisulfonate of biphenyl benzene, said agent being present in amount up to 3.5% by weight of said solution.

3. A nickel plating bath comprisingessentially a water solution of nickel sulfate, nickel chloride and boric acid, containing as an organic brightening agent a mixture of polysulfonates of M hydrogenated isomeric biphenyl benzenes, said agent being present in amount up' to 3.5% by weight of said solution.

4. A process of nickel plating comprising electro-depositing nickel from an essentially water 46 solution of nickel sulfate, nickel chloride and boric acid, said solution containing as an organic brightening agent a mixture of polysulfonates' of isomeric biphenyl benzenes, said agent being present in said solution in amount 'up to 3.5% by weight.

5. A process of nickel plating comprising electro-depositing nickel from an essentially water solution of nickel sulfate, nickel chloride and boric acid, said solution containing as an organic brightening agent, a mixture of trisulfonates of hydrogenated hydrocarbons, said hydrocarbons consisting of isomeric biphenyl benzenes boiling above 369 C., said agent being present in amount up to 3.5% by weight of said solution.

- MILTON KOSMIN. 

